Class XI | CHAPTER 2
Software Concepts
Hardware and Software
A computer consists of both hardware and
software and both are equally important for the working of the computer system.
The electronic components of a computer system that we can see and touch are
called hardware. Software is a general
term used for computer programs that control the operations of the computer. A program is a sequence of instructions that
perform a particular task. A set of
programs form software. It is the software which gives hardware its capability.
Hardware is of no use without software and software cannot be used without
hardware.
Types of Software
Software can be broadly are categorized as:
System Software
Application Software
Utility Software
System Software
System Software is the software that is
directly related to coordinating computer operations and performs tasks
associated with controlling and utilizing computer hardware. These programs
assist in running application programs and are designed to control the
operation of a computer system. System software directs the computer what to
do, when to do and how to do. System software can be further categorized into
Operating System
Language TranslatorsOperating System
An Operating system is the most important
system software. It is a set of programs that control and supervise
the hardware of a computer and also provide
services to application software,
programmers and users. It
manages all hardware and
software, input, output and
processing activities within
the computer system,
the flow of information to and
from the processor, sets priorities for handling different tasks, and so on. Without
operating system a computer cannot do anything useful. When a computer is
switched on, the operating system is the first program that is loaded onto its
memory. A user cannot communicate directly with the computer hardware, so the
operating system acts as an interface between the user and the computer
hardware. Some of the popular operating systems used in personal computers are
DOS, Windows, UNIX, Linux, Solaris, etc. An
operating system can be a Single User
or a Multiuser operating system.
A single user operating
system allows only
one user to
work at any
time but a multiuser
operating system allows
two or more
users to use a powerful computer
at the same time.
For example Windows
7 is a
single user operating
system while Linux
is a multiuser operating system.
Need for an Operating System
Operating system provides a platform, on
top of which, other programs, called application programs can run. As discussed
before, it acts as an interface between the computer and the user. It is
designed in such a manner that it operates controls and executes various
applications on the computer. It also allows the computer to manage its own
resources such as memory, monitor, keyboard, printer etc.
Our choice of operating system, therefore,
depends to a great extent on the CPU and the other attached devices and the applications
we want to run. The operating system controls
the various system hardware and software resources and allocates them to the
users or programs as per their requirement.
Functions of an Operating System
An operating system has variety of functions
to perform. Some of the prominent functions of an operating system can be
broadly outlined as:
Processor Management: This deals with management of the Central Processing Unit (CPU). The
operating system takes care of the allotment of CPU time to different
processes. This is called scheduling. Two types of scheduling techniques are
employed by an operating system:
·
Priority Scheduling: Each task is given CPU time according to the priority assigned to
that task. The program with higher priority will be given CPU time before a
program with lower priority. The CPU executes the task till it is completed or
there is some interrupt request i.e. till the time operating system has
to stop (interrupt)
the current task
due to an
unavoidable job request. The
major drawback of Priority scheduling is that even a small job has to wait for
a long time when a long duration job with higher priority is being executed.
·
Round Robin Scheduling: This type of scheduling technique is also known as Time Sharing
Scheduling. In this, each program or task is given a fixed amount of time to
execute. The CPU continues with the execution till either the allotted time is
over or there is some
interrupt request or
the task is completed before the allotted time. If the
task is not completed at the end of the
allotted time, it
is put at
the end of
the queue. So each task gets its
allotted share of CPU time. This
scheduling technique improves the response time and provides an interactive
environment. Hence time sharing operating system is very useful in network
environment as each user is allowed to share the network resources.
Device Management: The Operating System communicates with hardware and the attached
devices and maintains a balance between them and the CPU. This is all the more
important because the CPU processing speed is much higher than that of I/O
devices. In order to optimize the CPU time, the operating system employs two
techniques - Buffering and Spooling.
·
Buffering: In this technique the temporary storage of input and output data is
done in Input Buffer and Output Buffer. Once the signal for input or output is
sent to or from the CPU respectively, the operating system through the device
controller moves the data from the input device to the input buffer and for the
output device to the output buffer. When the signal is sent to/from the
operating system to the respective device controllers, the program doesn’t wait
rather it returns to its processing. In case of input, if the buffer is full,
the operating system sends a signal to the program which processes the data
stored in the buffer. When the buffer becomes empty, the program informs
the operating system
which reloads the
buffer and the input
operation continues. Similarly for output when the program being
executed has to display some output, it fills the buffer and then informs the
operating system. Thereafter the
operating system empties
the buffer by sending
data to the
output device and
in the meantime the
program fills another buffer.
This technique is called overlapped processing. This is because
while the operating
system reloads one
buffer, the executing program doesn’t
stop as it
is able to retrieve/fill data
from/in another buffer.
·
Spooling (Simultaneous
Peripheral Operation on
Line): This
is a device management technique
used for processing
of different tasks on
the same input/output device. Say
for example there are various users on a network sharing the same printer. At
one point of
time more than
one user might give print command. The speed of the
printer is very slow as compared to the CPU processing. So the operating system
temporarily stores the data of every user on the hard disk of the computer to
which the printer is attached. The individual users need not wait for the
printing process to be complete. Instead the operating system sends the data
from to hard disk to the printer one by one.
Memory management: In a computer, both the CPU and the I/O devices interact with the
memory. When a program needs to be executed it is loaded onto the main memory
till the execution is complete. Thereafter that memory space is freed and is
available for other programs. The common
memory management techniques used by the operating system are Partitioning and
Virtual Memory.
·
Partitioning: The total memory is divided into various partitions of same size or
different sizes. This helps to accommodate number of programs in the memory. The partition can be fixed i.e. remains same for all
the programs in the
memory or variable
i.e. memory is allocated
when a program is
loaded on to
the memory. The later approach causes less wastage of
memory but in due course of time, it may become fragmented.
·
Virtual Memory: This is a technique used by the operating system by virtue of which
the user can load the programs
which are larger
than the main memory of the computer. In this
technique the program is executed even if the complete program is not loaded on
to the main memory. The operating system divides the main memory into equal
sizes called pages. A part of the program resides in the main memory and is
called the active set. The rest is in the secondary storage device in
the form of tracks/sectors or blocks. With the
help of Page
Map Tables (PMT),
the operating system
keeps track which page of main
memory is storing which block of secondary memory. A virtual address (which is
not the real physical address) is mapped either to the main memory or the
secondary memory. Hence virtual memory
allows more programs and even larger programs to be executed in the main memory
leading to efficient memory utilization.
File Management: The operating System manages the files, folders and directory
systems on a computer. Any data on a
computer is stored in the form of files and the operating system keeps
information about all of them
using File Allocation Table (FAT). The FAT
stores general information
about files like
filename, type (text or
binary), size, starting
address and access
mode (sequential/indexed
sequential/direct/relative). The file
manager of the
operating system helps
to create, edit, copy,
allocate memory to the files
and also updates the
FAT. The operating system also
takes care that files are opened with proper access rights to read or edit
them.
Types of Operating System
OS are classified into the following types
depending on their capability of processing
Single User and Single Task
OS: It is used on a standalone single computer for
performing a single task. Operating
systems for Personal Computers (PC) are single-user OS. Single user OS are
simple operating system designed to manage one task at a time. MS-DOS is an
example of single user OS.
Multiuser OS is used in mini computers or mainframes that allow same data and
applications to be accessed by multiple users at the same time. The users can
also communicate with each other. Linux and UNIX are examples of multiuser OS.
Multiprocessing OS have two
or more processors
for a single
running process. Processing takes
place in parallel
and is also
called parallel processing. Each processor works on different parts of
the same task, or, on two or more different tasks. Since
execution takes place
in parallel, they
are used for
high speed execution, and to
increase the power of computer. Linux, UNIX and Windows 7 are examples of
multiprocessing OS.
Time sharing
Operating System: It allows
execution of more
than one tasks
or processes concurrently. For
this, the processor
time is divided
amongst different tasks. This
division of time
is also called
time sharing. The
processor switches rapidly between
various processes. After the stipulated time is over, the CPU shifts to next
task in waiting,
So this type
of operating system
employs round robin scheduling technique. The system
switches rapidly from one user to another but still each
user feels that
it is getting
a dedicated CPU
time. Virtual Memory techniques are
used in this
type of operating
system. For example,
the user can listen to music on the computer while
writing an article using a word processing software. The
user can switch
between the applications
and also transfer
data between them. Time
sharing operating system
can be both
single user and multiuser. Windows
95 and all
later versions of
Windows are examples
of multitasking OS.
Real Time Operating System: It is a multitasking
operating system designed for real time applications like robotics. In this
type of operating system, the tasks have to be done within a fixed deadline.
System performance is good if task is finished within this deadline. If
it is not
done, the situation
is called Deadline
Overrun. Lesser the deadline
over run, better
is the system
efficiency. Hence Real
Time operating systems depend
not only on
the logical result
of the computation
but also on the time in which the results are produced.
Distributed Operating
System:
On a network
data is stored
and processed on multiple
locations. The Distributed
Operating System is
used on networks
as it allows shared
data/files to be
accessed from any
machine on the
network in a transparent manner. We can insert and
remove the data and can even access all the input and
output devices. The
users feel as
if all data
is available on
their workstation itself.
Interactive Operating
System: This is
the operating system
that provides a Graphic User
Interface (GUI) through
which the user
can easily navigate
and interact. The computer responds almost immediately after an
instruction has been entered, and the
user can enter
new instructions after
seeing the results
of the previous instructions.
Commonly Used Operating Systems
Some of the commonly used operating systems
are discussed below:
1.
Windows: Microsoft launched Windows 1.0 operating system in 1985 and since
then Windows has ruled the world’s software market. It is a GUI (Graphic User Interface) and
various versions of Windows have been launched like Windows 95, Windows
98, Win NT,
Windows XP, Windows
7 and the
latest being Windows 8.
2.
Linux: Linux is a free and open
software which means it is freely available for use and since its source code
is also available so anybody can use it,
modify it and redistribute it.
It can be downloaded
from www.linux.org. It
is a very popular operating system used and
supported by many companies. The defining component of this operating system is
the Linux kernel.
3.
BOSS (Bharat
Operating System Solutions): This
is an Indian
distribution of GNU/Linux. It consists
of Linux operating
system kernel, office
application suite, Bharateeya OO, Internet
browser (Firefox), multimedia
applications and file sharing.
4.
UNIX: It is
a multitasking, multiuser
operating system originally
developed in 1969 at Bell Labs.
It was one of the first operating systems developed in a high level language,
namely C. Due to its portability, flexibility and power, UNIX is widely
being used in
a networked environment.
Today, ”UNIX” and
"Single UNIX Specification" interface are owned and
trademarked by The Open Group. There
are many different varieties
of UNIX, although
they share common similarities, the most popular being
GNU/Linux and Mac OS X.
5.
Solaris: It is a free Unix based operating system introduced by Sun
Microsystems in 1992. It is now also known as Oracle Solaris. Solaris is registered
as compliant with Single UNIX
Specification. It is
quite scalable and
is used on
virtual machines.
Mobile
Operating Systems (Mobile OS)
It is the
operating system that operates on digital mobile devices like smart phones and
tablets. It extends the features of a normal operating system for personal
computers so as to include
touch screen, Bluetooth,
WiFi, GPS mobile
navigation, camera, music player
and many more.
The most commonly
used mobile operating
systems are – Android and Symbian.
Android: It is a Linux derived Mobile OS released on 5th November
2007 and by 2011 it had more than 50% of the global Smartphone market
share. It is Google’s open and free
software that includes an operating system, middleware and some key
applications for use on mobile devices. Android applications are quiet user
friendly and even one can easily
customize the Smartphone
with Android OS.
Various versions of
Android OS have been released
like 1.0, 1.5, 1.6, 2. x, 3.0 etc. Most Android phones use the 2.x release
while Android 3.0 is
available only for tablets.
The latest Android
version released is 4.2.2. The Android releases have dessert
inspired codenames like Cupcake, Honeycomb, Ice Cream sandwich and Jelly Bean.
Symbian: This Mobile OS by Nokia (currently being maintained by Accenture)
designed for smartphones. It offers high
level of functional integration between communication and personal information
management. It has an integrated mail box and it completely facilitates the
usage of all
Google applications in
your smartphone easily.
Symbian applications are easy to shut down as compared to Android applications. Various versions like S60 series, S80 series,
S90 series, Symbian Anna etc have been released. The latest Symbian releases
(Symbian Belle) can support 48 languages.
Language Processors
We know that computer understands
instructions in machine code, i.e. in the form of 0s and 1s. It is difficult
for us to write computer program directly in machine code. The programs are
written mostly in
high-level languages, i.e.
BASIC, C++, Python
etc. A program written
in any high-level
programming language (or
written in assembly language) is called the Source
Program or Source Code.
The source code cannot be executed directly
by the computer. The source code must be converted into machine language to be
executed. The program translated into machine code is known as Object Program
or Object code.
The special translator system software that
is used to translate the program written in high-level language
(or Assembly language)
into machine code
is called language processor or translator program.
The language processors can be any of the
following three types- Assembler, Compiler and Interpreter.
Assembler
The Assembler
is used to
translate the program
written in Assembly
language into machine code.
The input of
Assembler is a
source program that
contains assembly language
instructions. The output generated by assembler is the object code or machine
code understandable by the computer.
Compiler
The language
processor that translates the complete source program as a whole in one go into
machine code is
called compiler. Some
of the examples
are C and
C++ compilers.
The program
translated into machine code is called the object program. The source code is
translated to object code successfully if it is free of errors. If there are
any errors in the source code, the
compiler specifies the
errors at the
end of compilation
with line numbers. The errors
must be removed before the compiler can successfully recompile the source code again.
Interpreter
The language
processor that translates
a single statement
of source program
into machine code and executes it immediately before moving on to the
next line is called an Interpreter. If there is an error in the statement the
interpreter terminates its translating process at that statement and displays
an error message.
Only after
removal of the error, the interpreter moves on to the next line for execution.
Utilities
A utility
software is one which provides certain tasks that help in proper maintenance
of the
computer. The job
of utility programs
is to keep
the computer system running smoothly. Nowadays
many utility softwares
are part of
the operating system
itself. Even if there is no utility software on your computer, the
computer works but with the right kind of utility software loaded, the computer
becomes more reliable and even its processing speed increases. Some of the
commonly use utility softwares are
antivirus, Disk defragmenter, backup, compression etc.
Antivirus
An antivirus is utility software which detects
and removes computer viruses. If the software
is not able to
remove the virus,
it is neutralized.
The antivirus keeps
a watch on the functioning of the computer system. If a virus is found
it may alert the user, flag the infected program or kill the virus. Some of the
common types of viruses are:
·
Boot Sector
Virus: A boot sector
virus displaces the boot record and copies itself to
the boot sector i.e. where the program to boot the machine is stored. So first
the virus is loaded on to the main memory and then the operating system.
Whenever a new disk is inserted the virus copies itself to the new disk. The
antivirus overwrites the correct boot record on the infected boot sector and
also cleans the bad sectors.
·
File Virus: A file virus generally attacks executable files.
They can attach to various locations of the original
file, replace code, fill in open spaces in the code, or create companion files
to work with an executable file. Most of the file viruses are memory resident
and wait in the memory until the user runs another program. While another program
is running, the virus replicates.
·
Macro Virus: This virus
infects an important
file called normal.dot
of MS Word. As soon
as the application
is opened the
virus gets activated.
It damages the formatting
of documents and
even may not
allow editing or saving of documents.
·
Trojan
Horse: It is a code
generally hidden in games or spreadsheets. Since they are
hidden, the program
seems to function
as the user
wants but actually it is
destroying the program. A Trojan horse does not require a host program to embed
itself. It is a complete program. Its main objective is to cause harm to the
data. They can create bad sectors on the disk, destroy file allocation tables
and cause the system to hang.
·
Worm: Worm
is a program
capable of replicating itself
on a computer network. A
worm also does
not require a
host as it
is a self
contained program. They generally
travel from one
computer to another
across communication links on a network. They generally disrupt routine
services.
Disk
Defragmenter
The memory is used in small chunks randomly.
Sometimes when a memory chunk of appropriate size is not available, the
operating system breaks or fragments the files resulting in slower access to
files. A disk defragmenter scans the hard disk for fragmented files and brings
all the fragments together.
Backup
Utility
This
utility is used
to create the copy of
the complete or
partial data stored
in a disk or CD on any other disk. In case the hard disk crashes or some
other system failure occurs, the files can be restored using backup software.
Compression
Utility
This utility is used to
compress large files. Compression is useful because it helps reduce resources
usage and the file transmission on the network becomes easier.
Disk
Cleaner
This utility scans for
file that have not been accessed/used
since long. Such files might be occupying huge amount of memory space. In that
case the Disk Cleaner utility prompts the user to delete such files so as to
create more space on the disk. If the files are important, the user might take
a backup before deleting them.
File
Management Tools
This utility
helps the user
in storing, indexing,
searching and sorting
files and folders on the system.
The most commonly used tool is the Windows Explorer and Google Desktop.
Application Software
Application software is bought by the user
to perform specific applications or tasks, say for example making a document or
making a presentation or handling inventory or managing the employee
database. Application software can be of
two types – General Purpose Application Software and Customized Application
software.
General Purpose Application Software
Some
of the application
software is made for
the common users
for day to day
applications and uses. These are also referred as Office Tools. The users may
use them in the manner
they want. Some
of the popular
types of general
purpose application software are
discussed below:
Word
Processor: Word processor is
a general purpose application software used to create
documents. It allows us to create , edit and format documents. We can use
different types of fonts of various sizes; underline or make bold a certain
part of the text. We
can add clipart
and other graphics
into the document.
Popular examples of Word
processing software are
Writer (Open Office)
and Microsoft Word.
We use word processing
software for various uses like writing a simple document to designing special
art effects. Since we can attach images
and different shapes, can use different
colors, even a
poster can be
designed using word
processing software.
Features like Mail
Merge, Macro has
further enhanced the
word processing software and made it very useful.
Presentation Tools: Presentation tools
is a general
purpose application software that lets us
create presentations on any topic. We can not only create a presentation
and add
slides into that
but also can
use different types
of background, fonts, animations, audio,
video, etc. We can add clipart and other graphics into
our document. Even audio video files can be added on to the presentations. Popular examples of
Presentation tools software
are Impress (open
office) and Microsoft Power Point.
Spreadsheet
Packages: Spreadsheet is general
purpose application software that lets us create and
store data in tabular form. Both text and numerical values can be entered in
that tables known as a spreadsheet. We can not only create a document and add data into
that but also
can create different
types of charts
and graphs based upon the
numerical data stored in that page. All common mathematical and statistical
formulae can be used on the numeric data.
Popular examples of Spreadsheet software are Calc (Open Office) and
Microsoft Excel.
Database
Management System: Database
Management System is general purpose application software
that lets us
create computer programs
that control the creation,
maintenance, and the
use of database
for an organization
and its end users. We can not only store data but can
also manage data in a database. We can also import and export the data to many
formats including Excel, Outlook, ASCII, dBase,
FoxPro, Oracle, SQL
Server, ODBC, etc.
Popular examples of Database Management System are Base (Open
Office) and Microsoft Access.Customized Software
Customized Software is one which is tailor
made as per the user’s requirement. Such type of software is customer specific.
It is made keeping in mind the individual needs of the user
and so are
also referred as
Domain Specific Tools.
Such software cannot
be installed and used by any other user/customer since the requirements
may differ. Some examples of customized software are discussed below:
Inventory Management
System & Purchasing
System: Inventory
Management System is generally used in
departmental stores or other organizations to keep the record of the stock of
all the physical resources. For Example, in a Computer store, it keeps
record of the
number of computers,
printers, printing sheet,
printer cartridge available. It
also helps to
place purchase orders,
bills, invoices etc. Various
reports as to
position of stock,
sales made in
a particular period,
profit earned etc. can be generated.
School Management
System: School
Management System (sometimes
called a School
Information System or SIS) is a system that manages all of a school's data in
a single, integrated
application. Having all
of the information
in a single
system allows schools to more easily connect data together. For example,
when viewing a student’srecord, the user can follow a link to the student’sclass, and from there a link to the
student’s teacher, and from
there a link
to the teacher's other
classes, and so on.
Payroll System: Payroll Management
System software is used by all
modern organizations to keep track of employees of the organization who
receives wages or salary. All
different payment amounts
are calculated by
the payroll software and
the record is
maintained. The software
keeps track of
personal records of employees
viz. name, address,
date of birth,
qualification, date of
joining etc. It also
keeps track of
professional record viz.
allowances, perks, income
tax, insurance etc. Different
reports, pay slips
etc can be
generated through this software.
Financial
Accounting: Financial accounting System is used to
prepare accounting information, maintain different
accounts ledger, and account books. It also helps an organization to make
budget.
Hotel Management: Hotel management
software refers to
management techniques used
in the hotel
sector. These can
include hotel administration, accounts, billing,
marketing, housekeeping, front
office or front
desk, food and beverage management, catering and
maintenance. Even advance bookings can be made through this software. Customers
can have a look at the hotel and the rooms before making bookings. At any point
of time the room availability, tariff for each type of room and even booking
status can be checked.
Reservation
System: Reservation System
is software used
to book (reserve)
air flights,
railway seats, movie
tickets, tables in
a restaurant, etc.
In the case
of a booking system, the inputs
are booking requests. The processing involves checking if bookings are
possible, and if so making the bookings. The outputs are booking
confirmations/rejections.
Weather Forecasting
system: This software makes
it possible to
forecast the weather for days and
even months in advance. The detailed weather reports can also be generated.Open Source Concepts
Software are mainly categorised into the
following categories based on their licenses:
1.
Proprietary
2.
Shareware
3.
Freeware
4.
Open source
5.
Free Software
Proprietary
We pay a supplier for a copy of the
software which these days may be supplied on physical media (disks) or
downloaded from the Internet. We get the permission to use the software on one
or sometimes more than one machines. Examples of this type of software include
Microsoft Office and Microsoft Windows.
Shareware
Shareware is basically a software for trial
purpose that the user is allowed to try for free, for a specified period of
time. It is usually downloaded from the Internet. When the trial period ends,
the software must be purchased or uninstalled.
Freeware
Freeware software is free of cost and is
usually bundled up with some operating system
or any other
software. Examples of
freeware include Microsoft
Internet Explorer which comes
bundled up with
any Microsoft operating
system. The author of the
freeware software is the owner of the software, though people may use it for
free. The source code is not available, so no modifications can be done.
Freeware should not be mistaken with Open Source Software or Free Software.
Open source
Open
Source Software (OSS)
is the software
which gives the
users freedom to run/use
the software for
any purpose and
in any manner.
They can be
used, modified and even redistributed. In simple terms it can be freely
used but it may not be free of charge. The source code is freely available to
the customer. Python, TuxPaint etc are examples of Open Source Software.
Free
Software
This type of software is freely accessible
and can be freely used, modified, copied or distributed by anyone. And no
licence fee or any other form of payment need to be made
for a free
software. The source
code is also accessible in
case of free softwares.
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